Method of making a multilayer piezoelectric substrate for acoustic wave device

ABSTRACT

A method of manufacturing a surface acoustic wave resonator includes forming or providing a support substrate layer, forming or providing piezoelectric layer of lithium niobate over the support substrate layer, and forming or providing an interdigital transducer electrode including a plurality of fingers over the piezoelectric layer. The piezoelectric layer formed or provided having a cut angle (e.g., the piezoelectric angle is cut so as to have a crystal orientation) that allows the surface acoustic wave device to operate as a longitudinally leaky surface acoustic wave device that confines the acoustic wave energy within the piezoelectric substrate and that has less propagation attenuation and a higher electromechanical coupling coefficient k2.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave devices, and moreparticularly to a method of making a multilayer piezoelectric substratesfor acoustic wave devices.

Description of Related Technology

An acoustic wave filter can include a plurality of acoustic resonatorsarranged to filter a radio frequency signal. Example acoustic wavefilters include surface acoustic wave (SAW) filters and bulk acousticwave (BAW) filters. A surface acoustic wave resonator of a surfaceacoustic wave filter typically includes an interdigital transducerelectrode on a piezoelectric substrate. A surface acoustic waveresonator is arranged to generate a surface acoustic wave.

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. Conventional surfaceacoustic wave filters need thinning the pitches of the interdigitaltransducer electrodes for achieving a higher frequency, but there areprocess limitations to such thinning. Conventionally, a substrate usinga longitudinally leaky SAW (LLSAW) filter may allow for higher acousticvelocity but has the drawback that the propagation attenuation of thesubstrate is higher

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In accordance with one aspect of the disclosure, a surface acoustic wavedevice is provided with a piezoelectric substrate having a cut angle(e.g., the piezoelectric angle is cut so as to have a crystalorientation) that allows the surface acoustic wave device to operate asa longitudinally leaky surface acoustic wave device that confines theacoustic wave energy within the piezoelectric substrate. The surfaceacoustic wave device has less propagation attenuation and a higherelectromechanical coupling coefficient k².

In accordance with one aspect of the disclosure, a longitudinally leakySAW device is provided having a multilayer substrate under theinterdigital transducer including a lithium niobate piezoelectricstructure (e.g., layer) underneath the interdigital transducer, and aquartz support substrate structure (e.g., layer) underneath the lithiumniobate piezoelectric structure.

In accordance with one aspect of the disclosure, a longitudinally leakySAW device is provided having a multilayer substrate under theinterdigital transducer including a lithium niobate piezoelectricstructure (e.g., layer) underneath the interdigital transducer, and asilicon support substrate structure (e.g., layer) underneath the lithiumniobate piezoelectric structure.

In accordance with one aspect of the disclosure, a longitudinally leakySAW device is provided having a multilayer substrate under theinterdigital transducer including a lithium niobate piezoelectricstructure (e.g., layer) underneath the interdigital transducer, and adiamond support substrate structure (e.g., layer) underneath the lithiumniobate piezoelectric structure.

In accordance with one aspect of the disclosure, a longitudinally leakySAW device is provided having a multilayer substrate under theinterdigital transducer including a lithium niobate piezoelectricstructure (e.g., layer) underneath the interdigital transducer, asilicon dioxide substrate structure (e.g., functional layer) underneaththe lithium niobate piezoelectric structure, and a silicon supportsubstrate structure (e.g., layer) underneath the silicon dioxidesubstrate structure.

In accordance with one aspect of the disclosure, a surface acoustic wavedevice is provided. The acoustic wave device comprises an interdigitaltransducer electrode including a plurality of fingers, a piezoelectriclayer of lithium niobate disposed below the interdigital transducerelectrode, and a support substrate layer disposed below thepiezoelectric layer. The piezoelectric layer has a cut angle defined byfirst, second and third Euler angles (ϕ₁, θ₁, ψ₁) so that the secondEuler angle θ₁ has a value of about 76<θ₁<86 degrees.

In accordance with another aspect of the disclosure, an acoustic wavefilter is provided. The acoustic wave filter comprises a surfaceacoustic wave resonator configured to filter a radio frequency signal.The surface acoustic wave resonator includes an interdigital transducerelectrode including a plurality of fingers, a piezoelectric layer oflithium niobate disposed below the interdigital transducer electrode,and a support substrate layer disposed below the piezoelectric layer.The piezoelectric layer has a cut angle defined by first, second andthird Euler angles (ϕ₁, θ₁, ψ₁) so that the second Euler angle θ₁ has avalue of about 76<θ₁<86 degrees.

In accordance with another aspect of the disclosure, a radio frequencymodule is provided. The radio frequency module comprises a packagesubstrate, a surface acoustic wave resonator configured to filter aradio frequency signal, and additional circuitry, the surface acousticwave resonator and additional circuitry disposed on the packagesubstrate. The surface acoustic wave resonator includes an interdigitaltransducer electrode including a plurality of fingers, a piezoelectriclayer of lithium niobate disposed below the interdigital transducerelectrode, and a support substrate layer disposed below thepiezoelectric layer. The piezoelectric layer has a cut angle defined byfirst, second and third Euler angles (ϕ₁, θ₁, ψ₁) so that the secondEuler angle θ₁ has a value of about 76<θ₁<86 degrees.

In accordance with another aspect of the disclosure, a wirelesscommunication device is provided. The wireless communication devicecomprises an antenna and a front end module including one or moresurface acoustic wave resonators configured to filter a radio frequencysignal associated with the antenna. Each surface acoustic wave resonatorincludes an interdigital transducer electrode including a plurality offingers, a piezoelectric layer of lithium niobate disposed below theinterdigital transducer electrode, and a support substrate layerdisposed below the piezoelectric layer. The piezoelectric layer has acut angle defined by first, second and third Euler angles (ϕ₁, θ₁, ψ₁)so that the second Euler angle θ₁ has a value of about 76<θ₁<86 degrees.

In accordance with another aspect of the disclosure, a method ofmanufacturing a surface acoustic wave resonator is provided. The methodcomprises forming or providing a support substrate layer, forming orproviding piezoelectric layer of lithium niobate over the supportsubstrate layer, and forming or providing an interdigital transducerelectrode including a plurality of fingers over the piezoelectric layer.The piezoelectric layer is formed or provided having a cut angle definedby first, second and third Euler angles (ϕ₁, θ₁, ψ₁) so that the secondEuler angle θ₁ has a value of about 76<θ₁<86 degrees.

In accordance with another aspect of the disclosure, a method ofmanufacturing a radio frequency module is provided. The method comprisesforming or providing a package substrate, forming or providing a surfaceacoustic wave resonator, and mounting the surface acoustic waveresonator and additional circuitry on the package substrate. Forming orproviding the surface acoustic wave resonator includes forming orproviding a support substrate layer, forming or providing piezoelectriclayer of lithium niobate over the support substrate layer, and formingor providing an interdigital transducer electrode including a pluralityof fingers over the piezoelectric layer. The piezoelectric layer isformed or provided having a cut angle defined by first, second and thirdEuler angles (ϕ₁, θ₁, ψ₁) so that the second Euler angle θ₁ has a valueof about 76<θ₁<86 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 is a cross sectional view of an existing surface acoustic wavedevice.

FIG. 2 is a cross-sectional view of a surface acoustic wave deviceaccording to an embodiment.

FIG. 3 is a cross-sectional view of a surface acoustic wave deviceaccording to an embodiment.

FIG. 4A is a graph of admittance versus frequency for the surfaceacoustic wave device of FIG. 2 .

FIG. 4B is a graph of resonator quality factor Q versus frequency forthe surface acoustic wave device of FIG. 2 .

FIG. 4C is a graph of loss portion of admittance versus frequency forthe surface acoustic wave device of FIG. 2 .

FIG. 5A is a graph of resonator quality factor Q versus lithium niobate2^(nd) Euler angle sweep for the surface acoustic wave device of FIG. 2for a quartz 3^(rd) Euler angle of 90 degrees.

FIG. 5B is a graph of resonator quality factor Q versus quartz Eulerangle sweep for the surface acoustic wave device of FIG. 2 for a quartz3^(rd) Euler angle of 90 degrees.

FIG. 5C is a graph of resonator quality factor Q versus lithium niobatethickness (hLN) sweep for the surface acoustic wave device of FIG. 2 fora quartz 3^(rd) Euler angle of 90 degrees.

FIG. 6A is a graph of resonator quality factor Q versus lithium niobate2^(nd) Euler angle sweep for the surface acoustic wave device of FIG. 2for a quartz 3^(rd) Euler angle of 0 degrees.

FIG. 6B is a graph of resonator quality factor Q versus quartz Eulerangle sweep for the surface acoustic wave device of FIG. 2 for a quartz3^(rd) Euler angle of 0 degrees.

FIG. 6C is a graph of resonator quality factor Q versus lithium niobatethickness (hLN) sweep for the surface acoustic wave device of FIG. 2 fora quartz 3^(rd) Euler angle of 0 degrees.

FIG. 7A is a graph of resonator quality factor Q versus lithium niobateEuler angle sweep for the surface acoustic wave device of FIG. 2 .

FIG. 7B is a graph of resonator quality factor Q versus lithium niobatethickness (hLN) sweep for the surface acoustic wave device of FIG. 2 .

FIG. 8A is a graph of resonator quality factor Q versus lithium niobateEuler angle sweep for the surface acoustic wave device of FIG. 2 .

FIG. 8B is a graph of resonator quality factor Q versus lithium niobatethickness (hLN) sweep for the surface acoustic wave device of FIG. 2 .

FIG. 9A is a graph of K2 versus lithium niobate thickness (hLN) fordifferent thicknesses of SiO2 (hSiO2) for the surface acoustic wavedevice of FIG. 3 .

FIG. 9B is a graph of resonator quality factor for resonant frequency(Qs) versus lithium niobate thickness (hLN) for different thicknesses ofSiO2 (hSiO2) for the surface acoustic wave device of FIG. 3 .

FIG. 9C is a graph of resonator quality factor for anti-resonantfrequency (Qp) versus lithium niobate thickness (hLN) for differentthicknesses of SiO2 (hSiO2) for the surface acoustic wave device of FIG.3 .

FIG. 10 is a schematic block diagram of a packaged module that includesa filter with an acoustic wave device according to an embodiment.

FIG. 11 is a schematic block diagram of a packaged module that includesa filter with an acoustic wave device according to another embodiment.

FIG. 12A is a schematic block diagram of a wireless communication devicethat includes a filter with an acoustic wave device according to anembodiment.

FIG. 12B is a schematic block diagram of a wireless communication devicethat includes a filter with an acoustic wave device according to anotherembodiment.

DETAILED DESCRIPTION

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

FIG. 1 is a cross-sectional view of an existing surface acoustic wavedevice 10. The surface acoustic wave device 10 includes a piezoelectriclayer 12 and an IDT electrode 14. The piezoelectric layer 12 can be alithium based piezoelectric layer. For example, the piezoelectric layer12 can be a lithium niobate (LiNbO3) layer. As another example, thepiezoelectric layer 12 can be a lithium tantalate (LiTaO3) layer. In thesurface acoustic wave device 10, the IDT electrode is over thepiezoelectric layer 12. The IDT electrode 14 can include molybdenum(Mo), tungsten (W), gold (Au), silver (Ag), copper (Cu), platinum (Pt),ruthenium (Ru), titanium (Ti), the like, or any suitable combinationthereof.

FIG. 2 shows a cross-sectional view of an embodiment of a surfaceacoustic wave (SAW) device 20. The SAW device 20 includes a substratestructure (e.g., layer, support substrate layer) 22, a piezoelectricstructure (e.g., layer) 23 over (e.g., disposed over, disposed adjacentto, disposed in contact with) the substrate structure 22, and aninterdigital transducer (IDT) electrode 24 over (e.g., disposed over,disposed adjacent to, disposed in contact with) the piezoelectricstructure 23. The IDT electrode 24 can extend a height h above thepiezoelectric structure 23 and have a pitch L between fingers 25 of theIDT electrode 24. The pitch L of the fingers 25 of the IDT electrode 24corresponds to a resonant frequency of the surface acoustic wave device20. The piezoelectric structure (e.g., layer) 23 can have a height H1that extends between (e.g., extends from) the substrate structure (e.g.,layer) 22 and the IDT electrode 24. The IDT electrode 24 can includemolybdenum (Mo), tungsten (W), gold (Au), silver (Ag), copper (Cu),platinum (Pt), ruthenium (Ru), titanium (Ti), the like, or any suitablecombination thereof.

In one implementation, the substrate structure (e.g., layer) 22 can beformed or provided. The piezoelectric structure (e.g., substrate, layer)23 can be formed or provided (e.g., disposed on, attached or adhered tothe substrate structure 22). The IDT electrode 24 can be formed orprovided (e.g., disposed on, attached or adhered to the piezoelectricstructure 23).

In one implementation, the substrate structure (e.g., layer) 22 caninclude (e.g., be made of, consist of) quartz. The substrate structure22 can have a relatively high impedance. An acoustic impedance of thesubstrate structure 22 can be higher than an acoustic impedance of thepiezoelectric structure (e.g., layer) 23. The piezoelectric structure(e.g., layer) 23 can include (e.g., be made of, consist of) lithiumniobate (LiNbO3), which has a negative temperature coefficient offrequency (TCF). In one example, the pitch (e.g., wavelength) L betweenfingers 25 of the IDT electrode 24 can be approximately 2 um, the heighth of the IDT electrode 24 can be approximately 0.08L (e.g., 0.08×thepitch L between fingers 25), such as 0.5L<H1<0.9L, and the height H1 ofthe second piezoelectric structure (e.g., layer) 23 can be 0.3L<H1<0.9L(e.g., between about 0.3×the pitch L between fingers 25 and about0.9×the pitch L between fingers 25), such as 0.5L<H1<0.9L, such as 0.7L(e.g., 0.7×the pitch L between fingers 25). In other implementations,the pitch L can have other suitable values. The height h of the fingers25 can be 0.06L<h<0.10L in some implementations. In one implementation,the SAW device 20 is a longitudinally leaky SAW (LLSAW) device.

The substrate structure 22 and/or the piezoelectric structure 23 canhave cut angles and/or thickness that advantageously confines theacoustic wave energy within the piezoelectric structure 22 that allowfor exciting the LLSAW having an acoustic velocity higher than a shearhorizontal SAW (SHSAW) or Rayleigh SAW, while having a lower propagationattenuation. The SAW device 20 can then advantageously provide a highvelocity, high Q resonator with high K².

In one example, the piezoelectric structure 23 can be made of lithiumniobate and have a cut angle (e.g., the piezoelectric structure 23 canbe cut to have a crystal orientation) defined by Euler angles (ϕ, θ, ψ),so that ϕ₁=0 degrees, θ₁=80 degrees and ψ₁=90 degrees, and the substratestructure 22 can be made of quartz and have a cut angle (e.g., thesubstrate structure 22 can be cut to have a crystal orientation) definedby Euler angles ϕ₂=0 degrees, θ₂=62 degrees and ψ₂=90 degrees. However,the piezoelectric structure 23 can have a second Euler angle of 76<θ₁<86degrees and the substrate structure 22 can have a second Euler angle of25<θ₁<70 degrees. In one example, the first and third Euler angles (ϕ,ψ) do not change. In on implementation, the first Euler angle ϕ for thesubstrate structure 22 and the piezoelectric structure 23 can be−15<ϕ<15 degrees. In one implementation, the second Euler angle ψ forthe substrate structure 22 and the piezoelectric structure 23 can be−15<ψ<15 degrees.

In another example, the piezoelectric structure 23 can be made oflithium niobate and the substrate structure 22 can be made of silicon.The piezoelectric structure 23 can have a cut angle (e.g., thepiezoelectric structure 23 can be cut to have a crystal orientation)defined by Euler angles (ϕ, θ, ψ), where the second Euler angle is76<θ₁<86 degrees and the height H1 of the piezoelectric structure (e.g.,layer) 23 is 0.4L<H1<0.8L, such as 0.7L. The Euler angles (ϕ, θ, ψ) forthe piezoelectric structure 23, when made of lithium niobate, are thesame as provided above, for example ϕ₁=0, θ₁=80 and ψ₁=90.

In another example, the piezoelectric structure 23 can be made oflithium niobate and the substrate structure 22 can be made of diamond.The height H1 of the piezoelectric structure (e.g., layer 23) is0.7L<H1<0.9L, such as 0.8L. The Euler angles (ϕ, θ, ψ) for thepiezoelectric structure 23, when made of lithium niobate, are the sameas provided above, for example ϕ₁=0, θ₁=80 and ψ₁=90.

FIG. 3 shows a cross-sectional view of an embodiment of a surfaceacoustic wave (SAW) device 30. The SAW device 30 includes a substratestructure (e.g., substrate, layer) 31, an additional structure (e.g.,substrate, functional layer) 32 over (e.g., disposed over, disposedadjacent to, disposed in contact with) the substrate structure 31, apiezoelectric structure (e.g., layer) 33 over (e.g., disposed over,disposed adjacent to, disposed in contact with) the additional structure32, and an interdigital transducer (IDT) electrode 34 over (e.g.,disposed over, disposed adjacent to, disposed in contact with) thepiezoelectric structure 33. The IDT electrode 34 can extend a height habove the piezoelectric structure 33 and have a pitch L between fingers35 of the IDT electrode 34. The pitch L of the fingers 35 of the IDTelectrode 34 corresponds to a resonant frequency of the surface acousticwave device 30. The piezoelectric structure (e.g., layer) 33 can have aheight H1 that extends between (e.g., extends from) the additionalstructure (e.g., layer) 32 and the IDT electrode 34. The additionalstructure (e.g., layer) 32 can have a height H2 that extends between(e.g., extends from) the substrate structure (e.g., layer) 31 and thepiezoelectric structure (e.g., layer) 33. The IDT electrode 34 caninclude molybdenum (Mo), tungsten (W), gold (Au), silver (Ag), copper(Cu), platinum (Pt), ruthenium (Ru), titanium (Ti), the like, or anysuitable combination thereof.

In one implementation, the substrate structure (e.g., layer) 31 can beformed or provided. The additional structure (e.g., substrate, layer) 32can be formed or provided (e.g., disposed on, attached or adhered to thesubstrate structure 31). The piezoelectric structure (e.g., layer) 33can be formed or provided (e.g., disposed on, attached or adhered to theadditional structure 32). The ID electrode 34 can be formed or provided(e.g., disposed on, attached or adhered to the piezoelectric structure33).

In one implementation, the substrate structure (e.g., layer) 31 caninclude (e.g., be made of, consist of) silicon, the additional structure(e.g., layer) 32 can include (e.g., be made of, consist of) silicondioxide (SiO2), and the piezoelectric structure (e.g., layer) 33 caninclude (e.g., be made of, consist of) lithium niobate (LiNbO3). Thesubstrate structure 31 can have a relatively high impedance. An acousticimpedance of the substrate structure 31 can be higher than an acousticimpedance of the piezoelectric structure (e.g., layer) 33. Theadditional structure (e.g., layer) 32 can have a lower acousticimpedance than the substrate structure (e.g., layer) 31. The additionalstructure (e.g., layer) 32 can increase adhesion between the substratestructure 31 and the piezoelectric structure 33 of the multi-layerpiezoelectric substrate. Alternatively or additionally, the additionalstructure (e.g., layer) 32 can increase heat dissipation in the SAWdevice 30 relative to the SAW device 20.

In one example, the pitch (e.g., wavelength) L between fingers 35 of theIDT electrode 34 can be approximately 2 um, the height h of the IDTelectrode 34 can be approximately 0.8L (e.g., 0.8×the pitch L betweenfingers 35), the height H1 of the piezoelectric structure (e.g., layer)33 can be 0.3L<H1<0.9L (e.g., between about 0.3×the pitch L betweenfingers 35 and about 0.9×the pitch L between fingers 35), such as0.3L<H1<0.5L, and the height H2 of the additional structure (e.g.,layer) 32 can be 0.3L<H2<0.7L (e.g., between about 0.3×the pitch Lbetween fingers 35 and about 0.7×the pitch L between fingers 35), suchas 0.3L<H2<0.5L. In one implementation, the SAW device 30 is alongitudinally leaky SAW (LLSAW) device.

The piezoelectric structure 33 can have cut angles and/or thickness thatadvantageously confines the acoustic wave energy within thepiezoelectric structure 33 that allow for exciting the LLSAW having anacoustic velocity higher than a shear horizontal SAW (SHSAW) or RayleighSAW, while having a lower propagation attenuation. In one example, thepiezoelectric structure 33 can be made of lithium niobate and have a cutangle (e.g., the piezoelectric structure 33 can be cut to have a crystalorientation) defined by Euler angles (ϕ, θ, ψ), so that ϕ₁=0 degrees,θ₁=80 degrees and ψ₁=90 degrees.

FIGS. 4A-4C show graphs of the performance of the SAW device 20, wherethe piezoelectric structure 23 is of lithium niobate and has a cut angle(e.g., crystal orientation) defined by Euler angles (ϕ, θ, ψ), so thatϕ₁=0 degrees, θ₁=80 degrees and ψ₁=90 degrees, and where the substratestructure 22 is of quartz and has a cut angle defined by Euler anglesϕ₂=0 degrees, θ₂=62 degrees and ψ₂=90 degrees, as compared with the SAWdevice 10 (e.g., baseline) where only a piezoelectric layer 12 oflithium niobate is provided below the IDT electrode 14. The Euler angles(ϕ, θ, ψ) for the piezoelectric layer 12 of the SAW device 10, when madeof lithium niobate, are ϕ₁=0 degrees, θ₁=80 degrees and ψ₁=90 degrees.The SAW device 10 can have a thickness for the piezoelectric layer 12between 100 nm and 350 nm with a roughened bottom surface, but wasmodeled with an infinite thickness for the comparison in FIGS. 4A-4C,which generally corresponds with such a bottom roughened structure.

FIG. 4A is a graph of admittance versus frequency, and shows that theoperating frequency is similar for the SAW device 20 as the SAW device10. Additionally, the k² or electro-mechanical coupling coefficient isapproximately the same for the SAW device 20 as the SAW device 10. FIG.4B is a graph of resonator quality factor Q versus frequency, and showsthat the SAW device 20 advantageously has a higher Q (see solid line)than the SAW device 10 (e.g., including a peak near the anti-resonantfrequency of approximately 3250 MHz). FIG. 4C is a graph of loss portionof admittance versus frequency, and shows that the SAW device 20 (seesolid line) advantageously has a lower loss values than the SAW device10 (see dashed line), for example between frequencies of approximately3150 to 3350 MHz and near the anti-resonant frequency of approximately3250 MHz.

FIGS. 5A-5C show graphs of parametric sweep results of the SAW device20, where the piezoelectric structure 23 is of lithium niobate and thesubstrate structure 22 is of quartz, and where the quartz third Eulerangle ψ₂ has a value of 90 degrees.

FIG. 5A shows a graph of parametric sweep results for the lithiumniobate 2^(nd) Euler angle θ₁ for the SAW device 20. The graph shows Qsor resonator quality factor Q of resonant frequency fs, Qp or resonatorquality factor Q of parallel resonant frequency fp, and k² or theelectro-mechanical coupling coefficient versus the lithium niobate2^(nd) Euler angle θ₁. The k² value determines the frequency distancebetween the resonant frequency (fs) and the parallel resonant frequency(fp) (e.g., anti-resonant frequency), and therefore determines theachievable bandwidth of the filter that includes the SAW device 20. Asshown in FIG. 5A, a 2^(nd) Euler angle θ₁ with a value of 76<θ₁<86degrees is preferred, with a peak at approximately θ₁=82 degrees, tohave a high Q value.

FIG. 5B shows a graph of parametric sweep results for the quartz 2^(nd)Euler angle θ₂ for the SAW device 20. The graph shows Qs or resonatorquality factor Q of resonant frequency fs and Qp or resonator qualityfactor Q of parallel resonant frequency fp versus the quartz 2^(nd)Euler angle θ₂. As shown in FIG. 5B, a 2^(nd) Euler angle θ₂ with avalue of 25<θ₂<70 degrees is preferred, with a peak at approximatelyθ₂=25 degrees, to have a high Q value.

FIG. 5C shows a graph of parametric sweep results for the lithiumniobate thickness H1 for the SAW device 20. The graph shows Qs orresonator quality factor Q of resonant frequency fs and Qp or resonatorquality factor Q of parallel resonant frequency fp versus lithiumniobate thickness H1 (e.g., hLN) as a function of the pitch L (e.g.,wavelength) between the fingers 25 of the IDT electrode 24. As shown inFIG. 5C, a thickness H1 (e.g., hLN) for lithium niobate (e.g., of thepiezoelectric structure 23) with a value of 0.5L<H1<0.9L (e.g.,0.5L<hLN<0.9L) is preferred, with a peak at approximately H1=0.7L, tohave a high Q value.

FIGS. 6A-6C show graphs of parametric sweep results of the SAW device20, where the piezoelectric structure 23 is of lithium niobate and thesubstrate structure 22 is of quartz, and where the quartz third Eulerangle ψ₂ has a value of 0 degrees. FIG. 6A shows a graph of parametricsweep results for the lithium niobate 2^(nd) Euler angle θ₁ for the SAWdevice 20. The graph shows Qs or resonator quality factor Q of resonantfrequency fs, and Qp or resonator quality factor Q of parallel resonantfrequency fp. As shown in FIG. 6A, both Qp and Qs remain low across arange of 2^(nd) Euler angle θ₁ with a value of 65<θ₁<90. FIG. 6B shows agraph of parametric sweep results for the quartz 2^(nd) Euler angle θ₂for the SAW device 20. The graph shows Qs or resonator quality factor Qof resonant frequency fs and Qp or resonator quality factor Q ofparallel resonant frequency fp versus the quartz 2^(nd) Euler angle θ₂.As shown in FIG. 6B, both Qp and Qs remain low across arrange of 2^(nd)Euler angle θ₂ with a value of 0<θ₂<180. FIG. 6C shows a graph ofparametric sweep results for the lithium niobate thickness H1 (e.g.,hLN) for the SAW device 20. The graph shows Qs or resonator qualityfactor Q of resonant frequency fs and Qp or resonator quality factor Qof parallel resonant frequency fp versus lithium niobate thickness H1(e.g., hLN) as a function of the pitch L (e.g., wavelength) between thefingers 25 of the IDT electrode 24. As shown in FIG. 6C, Qs and Qpremain low across a range of thickness H1 (e.g., hLN) for lithiumniobate (e.g., of the second piezoelectric structure 23) having a valueof 0<H1<2.0L. Therefore, a quartz third Euler angle ψ₂ of 0 degreesresults in a low Q value and is not preferred.

FIGS. 7A-7B show graphs of parametric sweep results of the SAW device20, where the piezoelectric structure 23 is of lithium niobate and thesubstrate structure 22 is of silicon.

FIG. 7A shows a graph of parametric sweep results for the lithiumniobate 2^(nd) Euler angle θ₁ for the SAW device 20. The graph shows Qsor resonator quality factor Q of resonant frequency fs, Qp or resonatorquality factor Q of parallel resonant frequency fp, and k² or theelectro-mechanical coupling coefficient versus the lithium niobate2^(nd) Euler angle θ₁. The k² value determines the frequency distancebetween the resonant frequency (fs) and the parallel resonant frequency(fp) (e.g., anti-resonant frequency), and therefore determines theachievable bandwidth of the filter that includes the SAW device 20. Asshown in FIG. 7A, a 2^(nd) Euler angle θ₁ with a value of 76<θ₁<86degrees is preferred, with a peak at approximately θ₁=80 degrees, tohave a high Q value.

FIG. 7B shows a graph of parametric sweep results for the lithiumniobate thickness H1 (e.g., hLN) for the SAW device 20. The graph showsQs or resonator quality factor Q of resonant frequency fs and Qp orresonator quality factor Q of parallel resonant frequency fp versuslithium niobate thickness H1 (e.g., hLN) as a function of the pitch L(e.g., wavelength) between the fingers 25 of the IDT electrode 24. Asshown in FIG. 7B, a thickness H1 (e.g., hLN) for lithium niobate (e.g.,of the piezoelectric structure 23) with a value of 0.4L<H1<0.8L (e.g.,0.4L<hLN<0.8L) is preferred, such as H1=0.7L (e.g., hLN=0.7L), to have ahigh Q value.

FIGS. 8A-8B show graphs of parametric sweep results of the SAW device20, where the piezoelectric structure 23 is of lithium niobate and thesubstrate structure 22 is of diamond.

FIG. 8A shows a graph of parametric sweep results for the lithiumniobate 2^(nd) Euler angle θ₁ for the SAW device 20. The graph shows Qsor resonator quality factor Q of resonant frequency fs, and Qp orresonator quality factor Q of parallel resonant frequency fp versus thelithium niobate 2^(nd) Euler angle θ₁. As shown in FIG. 8A, the Qp andQs values do not change significantly across a 2^(nd) Euler angle θ₁range of 60<θ₁<90 degrees and Qp remains high across the entire range.

FIG. 7B shows a graph of parametric sweep results for the lithiumniobate thickness H1 (e.g., hLN) for the SAW device 20. The graph showsQs or resonator quality factor Q of resonant frequency fs and Qp orresonator quality factor Q of parallel resonant frequency fp versuslithium niobate thickness H1 (e.g., hLN) as a function of the pitch L(e.g., wavelength) between the fingers 25 of the IDT electrode 24. Asshown in FIG. 8B, a thickness H1 (e.g., hLN) for lithium niobate (e.g.,of the piezoelectric structure 23) with a value of 0.7L<H1<0.9L (e.g.,0.7L<hLN<0.9L) is preferred, such as H1=0.8L (hLN=0.8L), to have a highQ value.

FIGS. 9A-9C show graphs of parametric sweep results of the SAW device30, where the substrate structure 31 is silicon, the additionalstructure (e.g., functional layer) 32 is silicon dioxide (SiO2) and thepiezoelectric structure 33 is lithium niobate. Graphs are provided fordifferent values of lithium niobate thickness (e.g., H1 or hLN) as afunction of the pitch L of the fingers 35 of the IDT electrode 34 (e.g.,H1 or hLN equal to 0.3L, 0.4L, 0.5L, 0.6L and 0.7L). FIG. 9A is a graphof K² versus lithium niobate thickness (e.g., H1 or hLN). FIG. 9B is agraph of resonator quality factor for resonant frequency (Qs) versuslithium niobate thickness (e.g., H1 or hLN). FIG. 9C is a graph ofresonator quality factor for anti-resonant frequency (Qp) versus lithiumniobate thickness (e.g., H1 or hLN). As shown in FIG. 9C, for athickness H2 or hSiO2 of 0.3L for the additional structure (e.g.,functional layer) 32, the thickness H1 (e.g., of lithium niobate or hLN)for the piezoelectric structure 33 is preferred to have a value between0.35L and 0.45L or between 0.55L and 0.7L to have a high Qp. For athickness H2 or hSiO2 of 0.4L for the additional structure (e.g.,functional layer) 32, the thickness H1 (e.g., of lithium niobate or hLN)for the piezoelectric structure 33 is preferred to have a value between0.30L and 0.45L or between 0.60L and 0.7L to have a high Qp. For athickness H2 or hSiO2 of 0.5L for the additional structure (e.g.,functional layer) 32, the thickness H1 (e.g., of lithium niobate or hLN)for the piezoelectric structure 33 is preferred to have a value between0.30L and 0.35L or between 0.45L and 0.55L to have a high Qp. For athickness H2 or hSiO2 of 0.6L for the additional structure (e.g.,functional layer) 32, the thickness H1 (e.g., of lithium niobate or hLN)for the piezoelectric structure 33 is preferred to have a value between0.35L and 0.45L to have a high Qp. For a thickness H2 or hSiO2 of 0.7Lfor the additional structure (e.g., functional layer) 32, the thicknessH1 (e.g., of lithium niobate or hLN) for the piezoelectric structure 33is preferred to have a value between 0.30L and 0.40L to have a high Qp.Additionally, the additional structure 32 of silicon dioxide (SiO2)between the substrate structure 31 of silicon and the piezoelectricstructure (e.g., layer) 33 of lithium niobate provides an improvement inTCF (e.g., the negative TCF decreases toward zero).

The surface acoustic wave device 20, 30 and/or other acoustic wavedevices disclosed herein can be included in a band pass filter. The bandpass filter can have a passband with a center frequency in a range from1.5 gigahertz (GHz) to 2.5 GHz. The center frequency can be anarithmetic mean or a geometric mean of a lower cutoff frequency of thepassband and an upper cutoff frequency of the passband. The centerfrequency in a range from 1.5 GHz to 2.2 GHz in certain instances. Thepassband can have a bandwidth in a range from 5 megahertz (MHz) to 100MHz in certain applications. The band pass filter can have a passbanddefined by a communication standard in which the passband is within afrequency range from 1.5 GHz to 2.5 GHz.

In some instances, the surface acoustic wave device 20, 30 and/or otheracoustic wave devices disclosed herein can be included in a band stopfilter having a center frequency in a range from 1.5 GHz to 2.5 GHz. Thestop band of the band stop filter can have a bandwidth in a range from 5MHz to 100 MHz in certain applications.

According to some other embodiments (not illustrated), a multi-layer IDTelectrode in accordance with any suitable principles and advantagesdisclosed herein can be implemented in a boundary wave resonator. Any ofthe principles and advantages disclosed herein can be implemented in anysuitable acoustic wave resonator that includes an IDT electrode.

The acoustic wave devices disclosed herein can be implemented in avariety of packaged modules. An example packaged module will now bedescribed in which any suitable principles and advantages of theacoustic wave resonators disclosed herein can be implemented. A packagedmodule can include one or more features of the packaged module of FIG.10 and/or the packaged module of FIG. 11 .

FIG. 10 is a schematic block diagram of a module 90 that includes afilter 92 with an acoustic wave device in accordance with any suitableprinciples and advantage disclosed herein. The module 90 includes thefilter 92 that includes an acoustic wave device, a switch 94, a poweramplifier 95, and a radio frequency (RF) coupler 96. The power amplifier95 can amplify a radio frequency signal. The switch 94 can selectivelyelectrically couple an output of the power amplifier 95 to the filter92. The filter 92 can be a band pass filter. The filter 92 can beincluded in a duplexer or other multiplexer. The RF coupler 96 can be adirectional coupler or any other suitable RF coupler. The RF coupler 96can sample a portion of RF power in a transmit signal path and providean indication of the RF power. The RF coupler 96 can be coupled to thetransmit signal path in any suitable point, such as between an output ofthe power amplifier 95 and an input to the switch 94. The module 90 caninclude a package that encloses the illustrated elements. The filter 92with the acoustic wave resonator can be disposed on a common packagingsubstrate 97 with the other illustrated elements of the module 90. Thepackaging substrate 97 can be a laminate substrate, for example.

FIG. 11 is a schematic block diagram of a module 100 that includesfilters 102 that include one or more acoustic wave devices in accordancewith any suitable principles and advantage disclosed herein. Asillustrated, the module 100 includes a power amplifier 95, a switch 94,filters 102, an antenna switch 104, a switch 105, a low noise amplifier106, and a control circuit 107.

The power amplifier 95 can receive a radio frequency signal from atransmit port TX. In some instances, a switch can electrically connect aselected one of a plurality of transmit ports to an input of the poweramplifier 95. The power amplifier 95 can operate in an envelope trackingmode and/or an average power tracking mode. The switch 94 can be amulti-throw radio frequency switch configured to electrically connect anoutput of the power amplifier 95 to one or more selected transmitfilters of the filters 102. The switch 94 can be a band select switcharranged to electrically connect the output of the power amplifier 95 toa transmit filter for a particular frequency band.

The filters 102 can be acoustic wave filters. One or more resonators inany of the filters 102 can include a multi-layer IDT electrode inaccordance with any suitable principles and advantages disclosed herein.In certain applications, all acoustic resonators of one or more filtersof the filters 102 include a multi-layer IDT electrode in accordancewith any suitable principles and advantages disclosed herein. Thefilters 102 can include a plurality of duplexers and/or othermultiplexers. Alternatively or additionally, the filters 102 can includeone or more standalone transmit filters and/or one or more standalonereceive filters. The filters 102 can include at least four duplexers insome applications. According to some other applications, the filters 102can include at least eight duplexers.

As illustrated, the filters 102 are electrically connected to theantenna switch 104. The antenna switch 104 can be a multi-throw radiofrequency switch arranged to electrically connect one or more filters ofthe filters 102 to an antenna port ANT of the module 100. The antennaswitch 104 can include at least eight throws in some applications. Incertain applications, the antenna switch 104 can include at least tenthrows.

A switch 105 can electrically connect a selected receive filter of thefilters to a low noise amplifier 106. The low noise amplifier 106 isarranged to amplify the received radio frequency signal and provide anoutput to a receive port RX. In some instances, another switch can beelectrically coupled between the low noise amplifier 106 and the receiveport RX.

The illustrated module 100 also includes a control circuit 107. Thecontrol circuit 107 can perform any suitable control functions for themodule 100.

FIG. 12A is a schematic block diagram of a wireless communication device110 that includes a filter 113 with an acoustic wave device inaccordance with one or more embodiments. The wireless communicationdevice 110 can be any suitable wireless communication device. Forinstance, a wireless communication device 110 can be a mobile phone,such as a smart phone. As illustrated, the wireless communication device110 includes an antenna 111, an RF front end 112, an RF transceiver 114,a processor 115, a memory 116, and a user interface 117. The antenna 111can transmit RF signals provided by the RF front end 112. The antenna111 can provide received RF signals to the RF front end 112 forprocessing.

The RF front end 112 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplex filters, oneor more filters of a multiplexer, one or more filters of a diplexer orother frequency multiplexing circuit, or any suitable combinationthereof. The RF front end 112 can transmit and receive RF signalsassociated with any suitable communication standard. Any of the acousticresonators disclosed herein can be implemented in filter 113 of the RFfront end 112.

The RF transceiver 114 can provide RF signals to the RF front end 112for amplification and/or other processing. The RF transceiver 114 canalso process an RF signal provided by a low noise amplifier of the RFfront end 112. The RF transceiver 114 is in communication with theprocessor 115. The processor 115 can be a baseband processor. Theprocessor 115 can provide any suitable base band processing functionsfor the wireless communication device 110. The memory 116 can beaccessed by the processor 115. The memory 116 can store any suitabledata for the wireless communication device 110. The processor 115 isalso in communication with the user interface 117. The user interface117 can be any suitable user interface, such as a display.

FIG. 12B is a schematic block diagram of a wireless communication device120 that includes a radio frequency front end 112 with a filter 113 anda diversity receive module 122 with a filter 123 according to anembodiment. The wireless communication device 120 is like the wirelesscommunication device 110 of FIG. 12A, except that the wirelesscommunication device 120 also includes diversity receive features. Asillustrated in FIG. 12B, the wireless communication device 120 includesa diversity antenna 121, a diversity module 122 configured to processsignals received by the diversity antenna 121 and including filters 123,and a transceiver 124 in communication with both the radio frequencyfront end 112 and the diversity receive module 122. The filter 103 caninclude one or more acoustic wave resonators having any suitable IDTelectrode disclosed herein. The filter 123 can include any can includeone or more acoustic wave resonators having any suitable IDT electrodedisclosed herein.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includessome example embodiments, the teachings described herein can be appliedto a variety of structures. Any of the principles and advantagesdiscussed herein can be implemented in association with RF circuitsconfigured to process signals in a frequency range from about 30kilohertz (kHz) to 300 gigahertz (GHz), such as in a frequency rangefrom about 450 MHz to 8.5 GHz. An acoustic wave resonator including anysuitable combination of features disclosed herein be included in afilter arranged to filter a radio frequency signal in a fifth generation(5G) New Radio (NR) operating band within Frequency Range 1 (FR1). Afilter arranged to filter a radio frequency signal in a 5G NR operatingband can include one or more acoustic wave resonators disclosed herein.FR1 can be from 410 MHz to 7.125 GHz, for example, as specified in acurrent 5G NR specification. One or more acoustic wave resonators inaccordance with any suitable principles and advantages disclosed hereincan be included in a filter arranged to filter a radio frequency signalin a fourth generation (4G) Long Term Evolution (LTE) operating band.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as packaged radio frequency modules, uplinkwireless communication devices, wireless communication infrastructure,electronic test equipment, etc. Examples of the electronic devices caninclude, but are not limited to, a mobile phone such as a smart phone, awearable computing device such as a smart watch or an ear piece, atelephone, a television, a computer monitor, a computer, a modem, ahand-held computer, a laptop computer, a tablet computer, a microwave, arefrigerator, a vehicular electronics system such as an automotiveelectronics system, a stereo system, a digital music player, a radio, acamera such as a digital camera, a portable memory chip, a washer, adryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” and words of similar import, when usedin this application, shall refer to this application as a whole and notto any particular portions of this application. Where the contextpermits, words in the above Detailed Description using the singular orplural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. Any suitable combination of theelements and acts of the various embodiments described above can becombined to provide further embodiments. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A method of manufacturing a surface acoustic waveresonator, the method comprising: forming or providing a supportsubstrate layer; forming or providing piezoelectric layer of lithiumniobate over the support substrate layer, the piezoelectric layer havinga cut angle defined by first, second and third Euler angles (ϕ₁, θ₁, ψ₁)so that the second Euler angle θ₁ has a value of about 76<θ₁<86 degrees;and forming or providing an interdigital transducer electrode includinga plurality of fingers over the piezoelectric layer.
 2. The method ofclaim 1 wherein forming or providing the support substrate layerincludes forming or providing the support substrate layer of a materialchosen from the group consisting of quartz, silicon and diamond.
 3. Themethod of claim 1 wherein the first Euler angle fi of the piezoelectriclayer is 0 degrees and the third Euler angle ψ₁ of the piezoelectriclayer is 90 degrees.
 4. The method of claim 1 wherein the piezoelectriclayer has a height H1 with a value of about 0.3L<H1<0.9L, where L is apitch between the fingers of the interdigital transducer electrode. 5.The method of claim 2 wherein the support substrate layer has a cutangle defined by first, second and third Euler angles (ϕ₂, θ₂, ψ₂) sothat the second Euler angle θ₂ has a value of about 25<θ₂<70 degrees. 6.The method of claim 5 wherein the first Euler angle ϕ₁ of the supportsubstrate layer is 0 degrees and the third Euler angle ψ₂ of the supportsubstrate layer is 90 degrees.
 7. The method of claim 1 furtherincluding forming a functional layer between the piezoelectric layer andthe support substrate layer.
 8. The method of claim 7 wherein thefunctional layer is a silicon dioxide layer having a thickness H2 with avalue of about 0.3L<H2<0.7L, where L is a pitch between the fingers ofthe interdigital transducer electrode.
 9. The method of claim 8 whereinthe piezoelectric layer has a thickness H1 with a value of about0.3L<H1<0.7L, where L is the pitch between the fingers of theinterdigital transducer electrode.
 10. A method of manufacturing a radiofrequency module, the method comprising: forming or providing a packagesubstrate; forming or providing a surface acoustic wave resonator,including forming or providing a support substrate later, forming orproviding a piezoelectric layer of lithium niobate over the supportsubstrate layer, the piezoelectric layer having a cut angle defined byfirst, second and third Euler angles (ϕ₁, θ₁, ψ₁) so that the secondEuler angle θ₁ has a value of about 76<θ₁<86 degrees, and forming orproviding an interdigital transducer electrode including a plurality offingers over the piezoelectric layer; and mounting the surface acousticwave resonator and additional circuitry on the package substrate. 11.The method of claim 10 wherein forming or providing the supportsubstrate layer includes forming or providing the support substratelayer of a material chosen from the group consisting of quartz, siliconand diamond.
 12. The method of claim 10 wherein the first Euler angle ϕ₁of the piezoelectric layer is 0 degrees and the third Euler angle ψ₁ ofthe piezoelectric layer is 90 degrees.
 13. The method of claim 10wherein the piezoelectric layer has a height H1 with a value of about0.3L<H1<0.9L, where L is a pitch between the fingers of the interdigitaltransducer electrode.
 14. The method of claim 11 wherein the supportsubstrate layer has a cut angle defined by first, second and third Eulerangles (ϕ₂, θ₂, ψ₂) so that the second Euler angle θ₂ has a value ofabout 25<θ₂<70 degrees.
 15. The method of claim 14 wherein the firstEuler angle fi of the support substrate layer is 0 degrees and the thirdEuler angle ψ₂ of the support substrate layer is 90 degrees.
 16. Themethod of claim 10 further including forming a functional layer betweenthe piezoelectric layer and the support substrate layer.
 17. The methodof claim 16 wherein the functional layer is a silicon dioxide layerhaving a thickness H2 with a value of about 0.3L<H2<0.7L, where L is apitch between the fingers of the interdigital transducer electrode. 18.The method of claim 17 wherein the piezoelectric layer has a thicknessH1 with a value of about 0.3L<H1<0.7L, where L is the pitch between thefingers of the interdigital transducer electrode.